1. Field of the Invention
The invention relates to a backlight module, more particularly to a backlight module which can provide a light output of uniform brightness.
2. Description of the Related Art
Referring to FIG. 1, a conventional side-edge and single-light-source type of backlight module 1 includes a light guide plate 11 in a shape of a wedge, a light source 12 provided adjacent to the light guide plate 11, a reflecting cover 13 covering the light source 12, and a reflector 114 disposed below the light guide plate 11. The light guide plate 11 includes a bottom face 111 having serrated microstructures (not shown) formed thereon, a top face 112, and a light entrance face 113 interconnecting the top and bottom faces 112, 111 and disposed adjacent to the light source 12. A light emitted by the light source 12 and reflected by the cover 13 enters the light guide plate 11 and exits from the top face 112 after undergoing total internal reflections.
However, the top face 112 of the light guide plate 11 has a relatively bright light output at an area adjacent to the light source 12 as compared to a remaining area of the top face 112 of the light guide plate 11. The light brightness of the top face 112 of the light guide plate 11 is not uniform, which in turn affects the quality of an image.
Referring to FIG. 2, in order to overcome the aforesaid disadvantage, a diffusion sheet 15 printed with a specific film 16 thereon is mounted on the top face 112 of the light guide plate 11. However, the cost for the specific film 16 is high. Therefore, a production cost is increased.
Additionally, the area of the top face 112 of the light guide plate 11 remote from the light source 12 can also have a relatively bright light output. While a shielding sheet 17 can be used to overcome the problem, it is not easy to install the shielding sheet 17 during the production of the backlight module 1, and the production cost is also increased thereby.